Resin composition, optical fiber, and method for manufacturing optical fiber

Abstract

A resin composition for a secondary coating of an optical fiber according to the present invention contains: a photopolymerizable compound containing urethane (meth)acrylamide; and a photopolymerization initiator, wherein the urethane (meth)acrylamide has a (meth)acrylamide group at least at one terminal of a urethane bond.

Description

Technical Field

[0001] The present disclosure relates to a resin composition for secondary coating of an optical fiber, an optical fiber, and a method for manufacturing an optical fiber. This application claims priority based on Japanese Application No. 2020-168361 filed on October 5, 2020, and incorporates all the descriptions set forth in the above-mentioned Japanese application.

Background Art

[0002] Generally, an optical fiber includes a coating resin layer for protecting a glass fiber which is an optical transmission body. The coating resin layer is composed of, for example, a primary resin layer in contact with the glass fiber and a secondary resin layer formed on the outer layer of the primary resin layer. A resin composition for secondary coating of an optical fiber is known to use a urethane (meth) acrylate which is a reaction product of a polyol, a diisocyanate, and a hydroxyl group-containing (meth) acrylate. For example, Patent Documents 1 to 3 describe resin compositions for secondary coating containing urethane (meth) acrylate.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

[0004] A resin composition for secondary coating of an optical fiber according to one embodiment of the present disclosure contains a photopolymerizable compound containing urethane (meth) acrylamide and a photoinitiator, and the urethane (meth) acrylamide has a (meth) acrylamide group at at least one end of the urethane bond.

[0005] An optical fiber according to one embodiment of the present disclosure comprises a glass fiber including a core and a cladding, a primary resin layer in contact with and covering the glass fiber, and a secondary resin layer covering the primary resin layer, wherein the secondary resin layer includes a cured product of the resin composition.

[0006] A method for manufacturing an optical fiber according to one embodiment of the present disclosure comprises a coating step of applying the resin composition to the outer circumference of a glass fiber including a core and cladding, and a curing step of curing the resin composition by irradiating it with ultraviolet light after the coating step. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a schematic cross-sectional view showing an example of an optical fiber according to this embodiment. [Modes for carrying out the invention]

[0008] [Issues this disclosure aims to address] The secondary resin layer of an optical fiber must have a high Young's modulus to enhance its microbend resistance. Furthermore, it is important that the secondary resin layer of an optical fiber has excellent scratch resistance to suppress appearance defects caused by surface abrasion. However, when increasing the manufacturing speed of optical fibers to improve productivity, the conventional resin compositions for secondary coatings described above tend to cure insufficiently, leaving room for improvement in the Young's modulus and scratch resistance of the resulting secondary resin layer.

[0009] This disclosure aims to provide a resin composition that can form a secondary resin layer for optical fibers that has a high Young's modulus and excellent trauma resistance, even when the manufacturing speed of optical fibers is high, and an optical fiber with excellent productivity.

[0010] [Effects of this disclosure] According to this disclosure, it is possible to provide a resin composition that can form a secondary resin layer of an optical fiber having a high Young's modulus and excellent trauma resistance, even when the optical fiber manufacturing speed is high, and an optical fiber with excellent productivity.

[0011] [Description of Embodiments in this Disclosure] First, the contents of the embodiments of this disclosure will be listed and explained. A resin composition for secondary coating of optical fibers according to one aspect of this disclosure contains a photopolymerizable compound containing urethane (meth)acrylamide and a photopolymerization initiator, wherein the urethane (meth)acrylamide has a (meth)acrylamide group at at least one end of the urethane bond. Such a resin composition can form a secondary resin layer with a high Young's modulus and excellent trauma resistance, even when the optical fiber manufacturing speed is high, and can improve the productivity of optical fibers.

[0012] From the viewpoint of forming a secondary resin layer with a higher Young's modulus and superior trauma resistance, the urethane (meth)acrylamide may include a urethane oligomer having a (meth)acrylamide group at one end of the urethane bond, a urethane oligomer having (meth)acrylamide groups at both ends of the urethane bond, or a mixture thereof.

[0013] A urethane oligomer having a (meth)acrylamide group at one end of a urethane bond may also include a urethane oligomer having a (meth)acrylamide group at one end of a urethane bond and a (meth)acryloyloxy group at the other end.

[0014] From the viewpoint of forming a secondary resin layer with a higher Young's modulus and superior trauma resistance, the number-average molecular weight of urethane (meth)acrylamide may be 500 or more and 6000 or less.

[0015] From the viewpoint of forming a secondary resin layer with a higher Young's modulus and superior scratch resistance, the content of urethane (meth)acrylamide may be 5 parts by mass or more and 60 parts by mass or less, based on 100 parts by mass of the total amount of the resin composition.

[0016] From the viewpoint of imparting appropriate toughness to the secondary resin layer, the photopolymerizable compound may further contain a (meth)acrylate.

[0017] From the viewpoint of imparting appropriate toughness to the secondary resin layer, the (meth)acrylate may contain a (meth)acrylate having a bisphenol skeleton.

[0018] [[ID=ll]]The optical fiber according to one aspect of the present disclosure includes a glass fiber including a core and a clad, a primary resin layer that contacts the glass fiber and coats the glass fiber, and a secondary resin layer that coats the primary resin layer. The secondary resin layer contains a cured product of the above-described resin composition. Such an optical fiber includes a secondary resin layer having a high Young's modulus and excellent abrasion resistance, and is excellent in productivity.

[0019] The method for manufacturing an optical fiber according to one aspect of the present disclosure includes a coating step of applying the above-described resin composition to the outer periphery of a glass fiber including a core and a clad, and a curing step of curing the resin composition by irradiating ultraviolet light after the coating step. Such a method for manufacturing an optical fiber can form a secondary resin layer having a high Young's modulus and excellent abrasion resistance even when the manufacturing speed is high, and can manufacture an optical fiber excellent in productivity.

[0020] [Details of Embodiments of the Present Disclosure] Specific examples of the resin composition and the optical fiber according to the present embodiment will be described while referring to the drawings as necessary. Note that the present disclosure is not limited to these examples, and is intended to be indicated by the claims and to include all modifications within the meaning and scope equivalent to the claims. In the following description, the same reference numerals are given to the same elements in the description of the drawings, and redundant descriptions are omitted. In the present specification, (meth)acrylamide means acrylamide or the corresponding methacrylamide. The same applies to similar expressions such as (meth)acrylate.

[0021] (Resin Composition) The resin composition according to this embodiment contains a photopolymerizable compound containing urethane (meth)acrylamide and a photoinitiator. The urethane (meth)acrylamide has a (meth)acrylamide group at at least one end of the urethane bond. Since the (meth)acrylamide group is more photopolymerizable than the (meth)acryloyloxy group, the urethane (meth)acrylamide has a faster curing rate than urethane (meth)acrylate and can improve the productivity of optical fibers.

[0022] From the viewpoint of forming a secondary resin layer having a higher Young's modulus and better scratch resistance, the urethane (meth)acrylamide may contain a urethane oligomer having a (meth)acrylamide group at one end of the urethane bond, a urethane oligomer having (meth)acrylamide groups at both ends of the urethane bond, or a mixture thereof.

[0023] From the viewpoint of forming a secondary resin layer having a higher Young's modulus and better scratch resistance, the urethane (meth)acrylamide preferably contains a urethane oligomer having (meth)acrylamide at both ends of the urethane bond. The urethane oligomer having (meth)acrylamide groups at both ends of the urethane bond may be a reaction product of a polyol, a diisocyanate, and N-hydroxyalkyl (meth)acrylamide.

[0024] The urethane oligomer having a (meth)acrylamide group at one end of the urethane bond may include a urethane oligomer having a (meth)acrylamide group at one end of the urethane bond and a (meth)acryloyloxy group at the other end. Such a urethane oligomer may be a reaction product of a polyol, a diisocyanate, N-hydroxyalkyl (meth)acrylamide, and a hydroxyl group-containing (meth)acrylate.

[0025] Examples of polyols include polyether polyols, polyester polyols, polycaprolactone polyols, polycarbonate polyols, polybutadiene polyols, and bisphenol A-ethylene oxide adduct diols. Examples of polyether polyols include polytetramethylene ether glycol, polyethylene glycol, and polypropylene glycol. These polyols may be used individually or in combination of two or more. From the viewpoint of easily adjusting the Young's modulus and elongation at break of the secondary resin layer, it is preferable to use at least one polyol selected from the group consisting of polypropylene glycol, polytetramethylene ether glycol, and polycarbonate polyol.

[0026] From the viewpoint of forming a tough secondary resin layer, the number-average molecular weight (Mn) of the polyol is preferably 300 to 2500, more preferably 400 to 2400, and even more preferably 500 to 2300. From a similar viewpoint, the urethane (meth)acrylamide preferably comprises structural units derived from a polyol with a number-average molecular weight of 300 to 2500, more preferably from a polyol with a number-average molecular weight of 400 to 2400, and even more preferably from a polyol with a number-average molecular weight of 500 to 2300.

[0027] Examples of diisocyanates include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, 1,5-naphthalene diisocyanate, norbornene diisocyanate, 1,5-pentamethylene diisocyanate, tetramethylxylylene diisocyanate, and trimethylhexamethylene diisocyanate. These diisocyanates may be used individually or in combination of two or more.

[0028] Examples of N-hydroxyalkyl(meth)acrylamides include N-hydroxymethyl(meth)acrylamide, N-hydroxyethyl(meth)acrylamide, and N,N-dimethylol(meth)acrylamide. These N-hydroxyalkyl(meth)acrylamides may be used individually or in combination of two or more. From the viewpoint of forming a secondary resin layer with a higher Young's modulus and superior trauma resistance, it is preferable to use N-hydroxyethylacrylamide as the N-hydroxyalkyl(meth)acrylamide.

[0029] Examples of hydroxyl group-containing (meth)acrylates include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, caprolactone (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 2-(meth)acryloyloxyethyl-2-hydroxyethyl phthalic acid, 2-hydroxy-O-phenylphenolpropyl (meth)acrylate, 2-hydroxy-3-methacrylate, trimethylolpropanedi (meth)acrylate, and pentaerythritol tri(meth)acrylate. These hydroxyl group-containing (meth)acrylates may be used individually or in combination of two or more. It is preferable to use at least one selected from the group consisting of 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 2-hydroxybutyl (meth)acrylate as the hydroxyl group-containing (meth)acrylate.

[0030] Methods for synthesizing urethane (meth)acrylamide include, for example, a method in which a polyol and diisocyanate are reacted to obtain a prepolymer having isocyanate groups at the ends (hereinafter also referred to as "NCO-terminated prepolymer"), and then N-hydroxyalkyl (meth)acrylamide (or hydroxyl-containing (meth)acrylate if necessary); a method in which diisocyanate and N-hydroxyalkyl (meth)acrylamide (or hydroxyl-containing (meth)acrylate if necessary) are reacted, and then a polyol is reacted; and a method in which a polyol, diisocyanate, and N-hydroxyalkyl (meth)acrylamide (or hydroxyl-containing (meth)acrylate if necessary) are reacted simultaneously.

[0031] When using a bifunctional polyol, it is preferable to react the hydroxyl group (OH) of the polyol with the isocyanate group (NCO) of the diisocyanate, and then react it with N-hydroxyalkyl (meth)acrylamide (or hydroxyl-containing (meth)acrylate if necessary). When using a trifunctional or more polyol, it is preferable to react the diisocyanate with N-hydroxyalkyl (meth)acrylamide (or hydroxyl-containing (meth)acrylate if necessary), and then react it with the polyol.

[0032] The preparation of urethane (meth)acrylamide will be explained below with specific examples. For example, polypropylene glycol is used as the polyol, 2,4-tolylene diisocyanate as the diisocyanate, N-hydroxyethylacrylamide as the N-hydroxyalkyl (meth)acrylamide, and 2-hydroxyethyl acrylate as the hydroxyl group-containing (meth)acrylate.

[0033] First, polypropylene glycol and 2,4-tolylene diisocyanate are reacted to synthesize an NCO-terminated prepolymer. Next, the NCO-terminated prepolymer is reacted with N-hydroxyethyl acrylamide and 2-hydroxyethyl acrylate to synthesize a urethane oligomer containing urethane acrylamide. The synthesized urethane oligomer can be represented as a mixture of urethane acrylamide of formulas (1) and (2) and urethane acrylate of formula (3). Formulas (4) to (6) below are by-products called adducts contained in the reactants and function as monomers. Am-(UIUP)nUIU-Am (1) Am-(UIUP)nUIU-Ac (2) Ac-(UIUP)nUIU-Ac (3) Am-UIU-Am (4) Am-UIU-Ac (5) Ac-UIU-Ac (6)

[0034] Here, Am represents a residue of N-hydroxyethylacrylamide, Ac represents a residue of 2-hydroxyethyl acrylate, U represents a urethane bond, I represents a residue of 2,4-tolylene diisocyanate, P represents a residue of polypropylene glycol, and n is an integer greater than or equal to 1.

[0035] When preparing urethane (meth)acrylamide, the addition of 2-hydroxyethyl acrylate is optional. If 2-hydroxyethyl acrylate is not added, (1) is produced as the main component and (4) as a by-product.

[0036] When reacting a polyol with a diisocyanate, the molar ratio (NCO / OH) of the isocyanate group (NCO) of the diisocyanate to the hydroxyl group (OH) of the polyol is preferably 1.1 to 6.0, more preferably 1.2 to 5.0, even more preferably 1.3 to 4.0, and particularly preferably 1.4 to 3.0. The NCO / OH ratio may also be 1.5 or higher, 1.7 or higher, or 1.9 or higher, and may be 2.5 or lower, 2.3 or lower, or 2.1 or lower. The molar ratio of the hydroxyl group of N-hydroxyalkyl(meth)acrylamide to NCO in the NCO-terminated prepolymer is preferably 0.10 to 1.15, more preferably 0.20 to 1.10, even more preferably 0.30 to 1.10, particularly preferably 0.40 to 1.10, and extremely preferably 0.50 to 1.10. The molar ratio of hydroxyl groups of N-hydroxyalkyl(meth)acrylamide to NCO in the NCO-terminated prepolymer may be 0.60 or more, 0.70 or more, 0.80 or more, or 0.90 or more, and may also be 1.09 or less, 1.08 or less, 1.07 or less, or 1.06 or less. The molar ratio of hydroxyl groups of hydroxyl group-containing (meth)acrylate to NCO in the NCO-terminated prepolymer is preferably 0 or more and 0.95 or less, more preferably 0 or more and 0.90 or less, even more preferably 0 or more and 0.80 or less, particularly preferably 0 or more and 0.70 or less, and extremely preferably 0 or more and 0.60 or less. The ratio of the total number of moles of hydroxyl groups in N-hydroxyalkyl(meth)acrylamide and hydroxyl group-containing (meth)acrylate to the number of moles of NCO in the NCO-terminated prepolymer is preferably 1.00 or more and 1.15 or less, and more preferably 1.03 or more and 1.10 or less.

[0037] For example, organotin compounds and amine compounds can be used as catalysts when synthesizing urethane (meth)acrylamide. Examples of organotin compounds include dibutyltin dilaurate, dibutyltin diacetate, dibutyltin maleate, dibutyltin bis(mercaptoacetate 2-ethylhexyl), dibutyltin bis(mercaptoacetate isooctyl), and dibutyltin oxide. These catalysts may be used individually or in combination of two or more. From the viewpoint of availability or catalytic performance, it is preferable to use dibutyltin dilaurate or dibutyltin diacetate as the catalyst.

[0038] The manganese (Mn) content of urethane (meth)acrylamide is preferably 500 to 6000, more preferably 600 to 5500, even more preferably 700 to 5000, and particularly preferably 1000 to 4000. When the Mn content of urethane (meth)acrylamide is 500 or more, it becomes easier to form a tough secondary resin layer, and when it is 6000 or less, it tends to be easier to increase the Young's modulus of the secondary resin layer. The Mn content of urethane (meth)acrylamide may be 1500 or more or 2000 or more, or 3500 or less or 3000 or less.

[0039] From the viewpoint of forming a secondary resin layer with a higher Young's modulus and superior scratch resistance, the content of urethane (meth)acrylamide is preferably 5 to 60 parts by mass, more preferably 10 to 55 parts by mass, and even more preferably 15 to 50 parts by mass, based on 100 parts by mass of the total amount of the resin composition.

[0040] The photopolymerizable compound according to this embodiment may further contain urethane (meth)acrylate. Urethane (meth)acrylate is a urethane oligomer having a (meth)acryloyloxy group. Urethane (meth)acrylate can be obtained by conventional methods by reacting a polyol, a diisocyanate, and a hydroxyl group-containing (meth)acrylate.

[0041] The polyols, diisocyanates, and hydroxyl group-containing (meth)acrylates used in the synthesis of urethane (meth)acrylates are not particularly limited, but may be selected from the compounds exemplified in the synthesis of urethane (meth)acrylamide described above.

[0042] The photopolymerizable compound according to this embodiment may further contain a photopolymerizable compound that does not have a urethane bond (hereinafter referred to as "monomer"). Examples of monomers include (meth)acrylic acid esters, N-vinyl compounds, and (meth)acrylamide compounds. The monomer may be a monofunctional monomer having one photopolymerizable ethylenically unsaturated group, or a polyfunctional monomer having two or more photopolymerizable ethylenically unsaturated groups.

[0043] From the viewpoint of imparting appropriate toughness to the secondary resin layer, it is preferable to use (meth)acrylic acid esters as monomers in the photopolymerizable compounds. Examples of (meth)acrylic acid esters include monofunctional (meth)acrylic acid esters and polyfunctional (meth)acrylic acid esters. A single (meth)acrylic acid ester may be used, or two or more may be used in combination.

[0044] Examples of monofunctional (meth)acrylic acid esters include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, isobutyl (meth)acrylate, n-pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, isoamyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, phenoxyethyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, benzyl (meth)acrylate, dicyclopentenyl (meth)acrylate, and dicyclopentenyl oxy Examples include ethyl (meth)acrylate, dicyclopentanyl (meth)acrylate, nonylphenol polyethylene glycol (meth)acrylate (for example, the product name "Aronics M-113" manufactured by Toagosei Co., Ltd.), nonylphenoxy polyethylene glycol (meth)acrylate, tri (meth)acrylate, 3-phenoxybenzyl (meth)acrylate, methylphenoxyethyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, phenoxy polyethylene glycol (meth)acrylate, m-phenoxybenzyl (meth)acrylate, 2-(2-ethoxyethoxy)ethyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl acrylate, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, ω-carboxy-polycaprolactone (meth)acrylate, etc.

[0045] Examples of polyfunctional (meth)acrylic acid esters include ethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, cyclohexanedimethanol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, hydroxypivalate neopentyl glycol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, diethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,12-dodecanediol di(meth)acrylate, 1,14-tetradecanediol di( Meth)acrylate, 1,16-Hexadecanediol di(meth)acrylate, 1,20-Eicosanediol di(meth)acrylate, Isopentyldiol di(meth)acrylate, 3-Ethyl-1,8-Octanediol di(meth)acrylate, Tricyclodecanol di(meth)acrylate, 9,9-Bis[4-(2-Hydroxyethoxy)phenyl]full orange (meth)acrylate, Bisphenol A epoxy di(meth)acrylate, Bisphenol F Poxydi(meth)acrylate, EO adduct di(meth)acrylate of bisphenol A, EO adduct di(meth)acrylate of bisphenol F, PO adduct di(meth)acrylate of bisphenol A, PO adduct di(meth)acrylate of bisphenol F, and difunctional (meth)acrylic acid esters such as "Epoxy Ester 40EM," "Epoxy Ester 70PA," "Epoxy Ester 200PA," and "Epoxy Ester 80MFA" manufactured by Kyoeisha Chemical Co., Ltd.;Trimethylolpropane tri(meth)acrylate, trimethyloloctanetri(meth)acrylate, trimethylolpropane polyethoxytri(meth)acrylate, trimethylolpropane polypropoxytri(meth)acrylate, trimethylolpropane polyethoxypolypropoxytri(meth)acrylate, tris[(meth)acryloyloxyethyl]isocyanurate, pentaerythritol tri(meth)acrylate, pentaerythritol polyethoxytetra(meth)acrylate Examples include trifunctional or more (meth)acrylic acid esters such as pentaerythritol polypropoxytetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and caprolactone-modified tris[(meth)acryloyloxyethyl]isocyanurate.

[0046] From the viewpoint of imparting appropriate toughness to the secondary resin layer, it is preferable that the (meth)acrylic acid ester contains a bisphenol skeleton-containing (meth)acrylate. The content of the bisphenol skeleton-containing (meth)acrylic acid ester may be 10 parts by mass or more, 15 parts by mass or more, or 20 parts by mass or more, based on 100 parts by mass of the total amount of the resin composition, and may be 70 parts by mass or less, 65 parts by mass or less, 60 parts by mass or less, 55 parts by mass or less, or 50 parts by mass or less.

[0047] The (meth)acrylic acid ester content may be 40 parts by mass or more, 45 parts by mass or more, 50 parts by mass or more, or 60 parts by mass or more, based on 100 parts by mass of the total amount of the resin composition, and may be 95 parts by mass or less, 90 parts by mass or less, 85 parts by mass or less, or 80 parts by mass or less.

[0048] Examples of N-vinyl compounds include N-vinylpyrrolidone, N-vinylcaprolactam, N-vinylmethyloxazolidinone, N-vinylimidazole, and N-vinyl-N-methylacetamide.

[0049] The curing speed of the resin composition can be further improved by including an N-vinyl compound in the photopolymerizable compound. The content of the N-vinyl compound is preferably 0 to 30 parts by mass, and more preferably 1 to 20 parts by mass, based on 100 parts by mass of the total amount of the resin composition.

[0050] Examples of (meth)acrylamide compounds include dimethyl(meth)acrylamide, diethyl(meth)acrylamide, (meth)acryloylmorpholine, hydroxymethyl(meth)acrylamide, hydroxyethyl(meth)acrylamide, isopropyl(meth)acrylamide, dimethylaminopropyl(meth)acrylamide, dimethylaminopropylacrylamide methyl chloride, diacetone acrylamide, (meth)acryloylpiperidine, (meth)acryloylpyrrolidine, (meth)acrylamide, N-hexyl(meth)acrylamide, N-methyl(meth)acrylamide, N-butyl(meth)acrylamide, N-methylol(meth)acrylamide, and N-methylolpropane(meth)acrylamide.

[0051] The curing speed of the resin composition can be further improved by including a (meth)acrylamide compound in the photopolymerizable compound. The content of the (meth)acrylamide compound is preferably 0 to 30 parts by mass, and more preferably 1 to 20 parts by mass, based on 100 parts by mass of the total amount of the resin composition.

[0052] The photopolymerization initiator according to this embodiment can be appropriately selected from known radical photopolymerization initiators and used. Examples of photopolymerization initiators include 1-hydroxycyclohexylphenyl ketone (trade name: Omnirad 184, manufactured by IGM Resins), 2,2-dimethoxy-2-phenylacetophenone (trade name: Omnirad 651, manufactured by IGM Resins), 2,4,6-trimethylbenzoyldiphenylphosphine oxide (trade name: Omnirad TPO, manufactured by IGM Resins), ethyl(2,4,6-trimethylbenzoyl)-phenylphosphine (trade name: Omnirad TPO-L, manufactured by IGM Resins), 2-benzyl-2-dimethylamino-4'-morpholinobutyrophenone (trade name: Omnirad 369, manufactured by IGM Resins), and 2-dimethylamino-2-(4-methylbenzyl)-1-(4-morpholin-4-ylphenyl)-butan-1-one (trade name: Omnirad 379, manufactured by IGM Resins). Examples include bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (trade name: Omnirad 819, manufactured by IGM Resins) and 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one (trade name: Omnirad 907, manufactured by IGM Resins).

[0053] The photopolymerization initiator may be used alone or in a mixture of two or more types. From the viewpoint of achieving superior rapid curing properties of the resin composition, it is preferable that the photopolymerization initiator contains at least one selected from 2,4,6-trimethylbenzoyldiphenylphosphine oxide and 1-hydroxycyclohexylphenyl ketone.

[0054] The content of the photopolymerization initiator is preferably 0.2 parts by mass or more and 5 parts by mass or less, more preferably 0.3 parts by mass or more and 4 parts by mass or less, and even more preferably 0.4 parts by mass or more and 3 parts by mass or less, based on 100 parts by mass of the total amount of the resin composition.

[0055] The resin composition according to this embodiment may further contain a photoacid generator, a leveling agent, an antifoaming agent, an antioxidant, an ultraviolet absorber, and the like.

[0056] As a photoacid generator, A + B - Onium salts having the structure shown may also be used. Examples of photoacid generators include sulfonium salts such as CPI-100P, CPI-110P (manufactured by Sunapro Co., Ltd.), Omnicat 270, and Omnicat 290 (manufactured by IGM Resins); and iodonium salts such as Omnicat 250 (manufactured by IGM Resins), WPI-113, WPI-116, WPI-124, WPI-169, and WPI-170 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.).

[0057] The viscosity of the resin composition according to this embodiment at 25°C is preferably 0.5 Pa·s to 10 Pa·s, and more preferably 1 Pa·s to 9 Pa·s, from the viewpoint of coating properties. The viscosity of the resin composition at 25°C can be measured using a B-type viscometer (Brookfield's "Digital Viscometer DV-II") under the conditions of spindle No. 18 and rotation speed of 10 rpm.

[0058] (Optical fiber) The optical fiber according to this embodiment comprises a glass fiber including a core and cladding, a primary resin layer in contact with and covering the glass fiber, and a secondary resin layer covering the primary resin layer.

[0059] Figure 1 is a schematic cross-sectional view showing an example of an optical fiber according to this embodiment. The optical fiber 10 comprises a glass fiber 13 including a core 11 and a cladding 12, and a coating resin layer 16 including a primary resin layer 14 provided on the outer circumference of the glass fiber 13 and a secondary resin layer 15 covering the primary resin layer 14.

[0060] The cladding 12 surrounds the core 11. The core 11 and cladding 12 mainly contain glass such as quartz glass. For example, the core 11 can be made of germanium-added quartz glass or pure quartz glass, and the cladding 12 can be made of pure quartz glass or fluorine-added quartz glass.

[0061] In Figure 1, for example, the outer diameter (D2) of the glass fiber 13 is approximately 100 μm to 125 μm, and the diameter (D1) of the core 11 constituting the glass fiber 13 is approximately 7 μm to 15 μm. The thickness of the coating resin layer 16 is typically approximately 22 μm to 70 μm. The thickness of each layer of the primary resin layer 14 and the secondary resin layer 15 may be approximately 5 μm to 50 μm.

[0062] When the outer diameter of the glass fiber 13 is approximately 125 μm and the thickness of the coating resin layer 16 is 60 μm or more and 70 μm or less, the thickness of each layer of the primary resin layer 14 and the secondary resin layer 15 may be approximately 10 μm to 50 μm. For example, the thickness of the primary resin layer 14 may be 35 μm and the thickness of the secondary resin layer 15 may be 25 μm. The outer diameter of the optical fiber 10 may be approximately 245 μm to 265 μm.

[0063] When the outer diameter of the glass fiber 13 is approximately 125 μm and the thickness of the coating resin layer 16 is between 24 μm and 48 μm, the thickness of each layer of the primary resin layer 14 and the secondary resin layer 15 may be approximately 8 μm to 38 μm. For example, the thickness of the primary resin layer 14 may be 25 μm and the thickness of the secondary resin layer 15 may be 10 μm. The outer diameter of the optical fiber 10 may be approximately 173 μm to 221 μm.

[0064] When the outer diameter of the glass fiber 13 is about 100 μm and the thickness of the coating resin layer 16 is between 22 μm and 37 μm, the thickness of each of the primary resin layer 14 and secondary resin layer 15 may be between 5 μm and 32 μm. For example, the thickness of the primary resin layer 14 may be 25 μm and the thickness of the secondary resin layer 15 may be 10 μm. The outer diameter of the optical fiber 10 may be between 144 μm and 174 μm.

[0065] The secondary resin layer 15 includes a cured product of the resin composition according to this embodiment. The secondary resin layer 15 can be formed by curing the resin composition according to this embodiment. Such a secondary resin layer 15 has a high Young's modulus and excellent trauma resistance.

[0066] From the viewpoint of improving the microbend resistance of the optical fiber, the Young's modulus of the secondary resin layer is preferably 800 MPa or higher at 23°C ± 2°C, more preferably 1000 MPa or higher, and even more preferably 1200 MPa or higher. The upper limit of the Young's modulus of the secondary resin layer is not particularly limited, but from the viewpoint of imparting appropriate toughness to the secondary resin layer, it may be 3000 MPa or less, 2500 MPa or less, or 2000 MPa or less at 23°C ± 2°C.

[0067] The Young's modulus of the secondary resin layer can be measured by the following method. First, the optical fiber is immersed in a mixed solvent of acetone and ethanol, and only the coating resin layer is extracted in a cylindrical shape. At this time, the primary resin layer and the secondary resin layer are integrated, but since the Young's modulus of the primary resin layer is 1 / 1000 to 1 / 10000 of that of the secondary resin layer, the Young's modulus of the primary resin layer can be ignored. Next, after removing the solvent from the coating resin layer by vacuum drying, a tensile test is performed at 23°C (tensile speed of 1 mm / min), and the Young's modulus can be determined using the secant formula for 2.5% strain.

[0068] From the viewpoint of improving the heat resistance of the secondary resin layer, the Tg of the secondary resin layer is preferably 70°C or higher, and more preferably 75°C or higher. From the viewpoint of suppressing the increase in transmission loss at low temperatures of the optical fiber, the Tg of the secondary resin layer is preferably 105°C or lower, and more preferably 95°C or lower.

[0069] The primary resin layer 14 can be formed by curing a resin composition containing, for example, a photopolymerizable compound including urethane (meth)acrylate, a photopolymerization initiator, etc. The resin composition forming the primary resin layer has a different composition from the resin composition for the secondary coating. The resin composition for the primary coating can be prepared using conventionally known techniques.

[0070] The resin composition for the primary coating may contain urethane (meth)acrylamide. Examples of urethane (meth)acrylamide include reaction products of a polyol, diisocyanate, and N-hydroxyalkyl (meth)acrylamide, and reaction products of a polyol, diisocyanate, N-hydroxyalkyl (meth)acrylamide, and methanol.

[0071] From the viewpoint of improving the microbend resistance of optical fibers, the Young's modulus of the primary resin layer is preferably 0.8 MPa or less at 23°C ± 2°C, and more preferably 0.5 MPa or less. If the Young's modulus of the primary resin layer exceeds 0.8 MPa, external forces are more easily transmitted to the glass fiber, and the increase in transmission loss due to microbending tends to increase.

[0072] In some cases, multiple optical fibers are arranged in parallel and integrated with a ribbon resin to form an optical fiber ribbon. The resin composition according to this disclosure can also be used as a ribbon resin. This improves the surface slipperiness and abrasion resistance when an external force is applied to the optical fiber ribbon.

[0073] (Manufacturing method for optical fibers) The method for manufacturing an optical fiber according to this embodiment includes a coating step of applying the resin composition according to this embodiment to the outer circumference of a glass fiber including a core and cladding, and a curing step of curing the resin composition by irradiating it with ultraviolet light after the coating step. In this embodiment, the resin composition is not applied directly to the glass fiber, but rather the resin composition for the primary coating is applied directly to the glass fiber. That is, in the coating step, a primary coating that is in contact with the glass fiber and a secondary coating that is not in contact with the glass fiber are formed by the resin composition according to this embodiment.

[0074] The optical fiber manufacturing method according to this embodiment, by using the resin composition according to this embodiment as the resin composition for secondary coating, makes it possible to form a secondary resin layer with a high Young's modulus and excellent trauma resistance even when the optical fiber manufacturing speed is high (for example, when the linear velocity is 3000 m / min or more), and thus enables the manufacture of optical fibers with excellent productivity. [Examples]

[0075] The following describes the results of evaluation tests using the examples and comparative examples related to this disclosure, and further explains this disclosure in detail. However, this disclosure is not limited to these examples.

[0076] [Synthesis of Urethane Acrylamide A for Secondary Resin Layers] (A-1) Polypropylene glycol with a manganese content of 600 (PPG600, manufactured by Sanyo Chemical Industries, Ltd., trade name: Sannix PP-600) and 2,4-tolylene diisocyanate (TDI) were mixed so that the molar ratio of NCO to OH (NCO / OH) was 2.0, and the mixture was reacted at 60°C for 1 hour to prepare an NCO-terminated prepolymer. Dibutyltin dilaurate was added as a catalyst at a concentration of 200 ppm relative to the final total charge. Next, HEAA was added to the NCO of the NCO-terminated prepolymer so that the molar ratio of N-hydroxyethylacrylamide (HEAA) to OH (HEAA / NCO) was 1.05, and the mixture was reacted at 60°C for 1 hour to obtain urethane acrylamide (A-1) with a manganese content of 2200.

[0077] (A-2) Mn2900 urethane acrylamide (A-2) was obtained in the same manner as the synthesis of (A-1) above, except that polypropylene glycol with Mn1000 (PPG1000, manufactured by Sanyo Chemical Industries, Ltd., product name: Sannix PP-1000) was used instead of PPG600.

[0078] (A-3) Except for using polypropylene glycol with a manganese content of 2000 (PPG2000, manufactured by Sanyo Chemical Industries, Ltd., product name: Sannix PP-2000) instead of PPG600, a urethane acrylamide with a manganese content of 5500 (A-3) was obtained in the same manner as the synthesis described in (A-1) above.

[0079] (A-4) Except for adding HEAA to the NCO-terminated prepolymer so that the molar ratio of HEAA's OH groups (HEAA / NCO) was 0.55, and adding HEA so that the molar ratio of 2-hydroxyethyl acrylate (HEA)'s OH groups (HEA / NCO) was 0.5, the synthesis was carried out in the same manner as in (A-3) above to obtain Mn5400 urethane acrylamide (A-4).

[0080] [Synthesis of urethane acrylate Y for secondary resin layer] (Y-1) PPG600 and TDI were mixed so that the molar ratio of NCO to OH (NCO / OH) was 2.0, and the mixture was reacted at 60°C for 1 hour to prepare an NCO-terminated prepolymer. Dibutyltin dilaurate was added as a catalyst at a concentration of 200 ppm relative to the final total charge. Next, HEA was added to the NCO of the NCO-terminated prepolymer so that the molar ratio of HEA to OH (HEA / NCO) was 1.05, and the mixture was reacted at 60°C for 1 hour to obtain Mn2200 urethane acrylate (Y-1).

[0081] (Y-2) Mn2900 urethane acrylate (Y-2) was obtained using the same method as the synthesis of (Y-1) above, except that PPG1000 was used instead of PPG600.

[0082] (Y-3) A urethane acrylate with Mn 5400 (Y-3) was obtained in the same manner as above (Y-1), except that PPG2000 was used instead of PPG600.

[0083] [Synthesis of Urethane Acrylamide Z for Primary Resin Layers] Polypropylene glycol with a manganese content of 3000 (PPG3000, manufactured by Sanyo Chemical Industries, Ltd., trade name: Sannix PP-3000) and TDI were reacted at 60°C for 1 hour to prepare an NCO-terminated prepolymer, such that the molar ratio of NCO to OH (NCO / OH) was 1.5. Dibutyltin dilaurate was added as a catalyst at a concentration of 200 ppm relative to the final total charge. Next, HEAA was added to the NCO of the NCO-terminated prepolymer so that the molar ratio of HEAA to OH (HEAA / NCO) was 0.65, and methanol was added so that the molar ratio of methanol to OH (MeOH / NCO) was 0.4. The mixture was reacted at 60°C for 1 hour to obtain urethane acrylamide Z with a manganese content of 11300.

[0084] (Measurement of Mn) The manganese (Mn) content of polyols is the value listed in each product catalog. The manganese content of urethane acrylamide and urethane acrylate was measured using a Waters ACQUITY APC RI system under the following conditions: sample concentration: 0.2% by mass THF solution, injection volume: 20 μL, sample temperature: 15°C, mobile phase: THF, organic solvent XT column: particle size 2.5 μm, pore size 450 Å, column inner diameter 4.6 × column length 150 mm + particle size 2.5 μm, pore size 125 Å, column inner diameter 4.6 × column length 150 mm + particle size 1.7 μm, pore size 45 Å, column inner diameter 4.6 × column length 150 mm, column temperature: 40°C, flow rate: 0.8 mL / min.

[0085] [Resin composition for secondary coating] As (meth)acrylic acid esters, bisphenol A epoxy di(meth)acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., trade name: Viscoat #540), isobornyl acrylate, and tripropylene glycol diacrylate were prepared. As photopolymerization initiators, 2,4,6-trimethylbenzoyl diphenylphosphine oxide (Omnirad TPO) and 1-hydroxycyclohexyl phenyl ketone (Omnirad 184) were prepared. Each component was mixed in the amounts (parts by mass) shown in Table 1 below to prepare resin compositions for secondary coating in each test example. Test Examples 1 to 6 correspond to examples, and Test Examples 7 to 9 correspond to comparative examples.

[0086] [Resin composition for primary coating] A resin composition for primary coating was prepared by mixing 70 parts by mass of urethane oligomer Z, 18 parts by mass of nonylphenol polyethylene glycol acrylate (manufactured by Toagosei Co., Ltd., trade name "Aronics M-113"), 10 parts by mass of N-vinylcaprolactam, 1 part by mass of Omnirad TPO, and 1 part by mass of 3-acryloxypropyltrimethoxysilane.

[0087] [Fabrication of optical fibers] A primary coating resin composition and a secondary coating resin composition were applied to the outer surface of a 125 μm diameter glass fiber 13. Next, the resin compositions were cured by irradiation with ultraviolet light to form a coating resin layer 16 comprising a primary resin layer 14 and a secondary resin layer 15, thereby fabricating an optical fiber 10. The thickness of the primary resin layer 14 was 35 μm, and the thickness of the secondary resin layer 15 was 25 μm. Optical fibers were fabricated at linear speeds of 2500 m / min, 3000 m / min, and 3500 m / min.

[0088] [Evaluation of optical fibers] (Young's modulus of the secondary resin layer) The optical fiber was immersed in a mixed solvent of acetone and ethanol, and only the coating resin layer was extracted in a cylindrical shape. Next, the solvent was removed from the coating resin layer by vacuum drying, and then a tensile test was performed at 23°C (tensile speed of 1 mm / min), and the Young's modulus was determined using the secant formula with 2.5% strain.

[0089] (Damage resistance of the secondary resin layer) For every 1000km of optical fiber produced, the amount of debris on the surface of the secondary resin layer on the production line was evaluated as "A" if it was less than 1g, and "C" if it was 1g or more.

[0090] [Table 1] [Explanation of Symbols]

[0091] 10 Optical Fibers 11 cores 12 clad 13. Glass fiber 14 Primary resin layer 15. Secondary resin layer 16. Coating resin layer

Claims

1. A glass fiber comprising a core and a cladding, A primary resin layer that is in contact with and covers the glass fiber, An optical fiber comprising a secondary resin layer covering the primary resin layer, The Young's modulus of the secondary resin layer is 860 MPa or more and 1700 MPa or less. The secondary resin layer comprises a cured product of the resin composition, The resin composition contains a photopolymerizable compound including urethane (meth)acrylamide and a photopolymerization initiator. The urethane (meth)acrylamide is an optical fiber having a (meth)acrylamide group at at least one end of the urethane bond.

2. The optical fiber according to claim 1, wherein the urethane (meth)acrylamide comprises a urethane oligomer having a (meth)acrylamide group at one end of the urethane bond, a urethane oligomer having (meth)acrylamide groups at both ends of the urethane bond, or a mixture thereof.

3. The optical fiber according to claim 2, wherein the urethane oligomer having a (meth)acrylamide group at one end of the urethane bond comprises a urethane oligomer having a (meth)acrylamide group at one end of the urethane bond and a (meth)acryloyloxy group at the other end.

4. The optical fiber according to any one of claims 1 to 3, wherein the number average molecular weight of the urethane (meth)acrylamide is 500 or more and 6000 or less.

5. The optical fiber according to any one of Claims 1 to 4, wherein the content of the urethane (meth)acrylamide in the resin composition is 5 parts by mass or more and 60 parts by mass or less, based on 100 parts by mass of the total amount of the resin composition.

6. The optical fiber according to any one of claims 1 to 5, wherein the photopolymerizable compound further comprises a (meth)acrylic acid ester.

7. The optical fiber according to claim 6, wherein the (meth)acrylic acid ester comprises a (meth)acrylate having a bisphenol skeleton.

8. A method for manufacturing an optical fiber according to any one of claims 1 to 7, A coating step of applying the resin composition to the outer circumference of the glass fiber, including the core and the cladding, A method for manufacturing optical fibers, comprising a curing step of curing the resin composition by irradiating it with ultraviolet light after the coating step.

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